panic on nested map

[Ruslan Orel]

I got a panic error if my struct has an nested map. Not sure but, i think it starts appear after go compiler updated. Now it 1.6.

reflect: Elem of invalid type
/usr/lib/go/src/runtime/panic.go:426 (0x42d659)
        gopanic: reflectcall(nil, unsafe.Pointer(d.fn), deferArgs(d), uint32(d.siz), uint32(d.siz))
/usr/lib/go/src/reflect/type.go:599 (0x5b3283)
        (*rtype).Elem: panic("reflect: Elem of invalid type")
/opt/project/src/github.com/fatih/structs/structs.go:535 (0x6cccd5)
        (*Struct).nested: v := val.Type().Elem()
/opt/project/src/github.com/fatih/structs/structs.go:120 (0x6c9c2e)
        (*Struct).FillMap: finalVal = s.nested(val)
/opt/project/src/github.com/fatih/structs/structs.go:84 (0x6c97db)
        (*Struct).Map: s.FillMap(out)
...

[Fatih Arslan]

Can you please provide a reproducible struct and case that I can test. Thanks.

[Ruslan Orel]

Thanks for quick reply. I used a next structure:

type WebhookModel struct {
	Id bson.ObjectId `json:"id" bson:"_id,omitempty"`
	Name string `json:"name" bson:"name" validate:"required,max=256"`
	Ip string `json:"ip" bson:"ip" validate:"required,ip"`
	Query string `json:"query" bson:"query" validate:"max=256"`
	Payload interface{} `json:"payload" bson:"payload"`
	CreatedAt time.Time `json:"createdAt" bson:"createdAt" validate:"required"`
}

Payload field could contain string or structured map. In case, when it's a simple map (ex. map[string]string {"test_param": "test_value"}) I got an error, described above

[Fatih Arslan]

Could you also fill the value that makes it panicing ? Just want to get as much information as it makes debugging easier. Thanks

[Ruslan Orel]

Ok. There are simpler example:

import (
	"github.com/fatih/structs"
	"log"
)

type WebhookModel struct {
	Name string `json:"name" bson:"name" validate:"required,max=256"`
	Ip string `json:"ip" bson:"ip" validate:"required,ip"`
	Query string `json:"query" bson:"query" validate:"max=256"`
	Payload interface{} `json:"payload" bson:"payload"`
}

model := WebhookModel{
	Name: "test",
	Ip: "127.0.0.1",
	Query: "",
	Payload: map[string]string {"test_param": "test_param"},
}

structToMap := structs.New(model)
structToMap.TagName = "bson"

//panic raised here
params := structToMap.Map()

log.Println(params)

[Ruslan Orel]

hi. i found a solution. don't know what other bugs it could born, but package's tests completed successfully. just remove the line, where the panic raised v := val.Type().Elem(). Looks like v already contains suitable value.

Upd: this solution omit iteration over map's structs. is it necessary at all?

[Fatih Arslan]

Thanks @russ666

I have a fix on my local branch. I just need to add some tests to be sure it doesn't break old tests. I'll push it when it's ready, you'll get notified when this get closed.

[Fatih Arslan]

This is now fixed in master. Thanks for the feedback again 👍